I always liked the "head anim" while reloading guns, I think the first game where this stuff has been implemented was Call Of Duty 2, actually almost all modern FPS implement it.
The anims of the weapons in D3 are good, but lack of this enhancement, so I decided to implement it.
Basically, the anim of the head is handled by a new bone in the weapon's view model, the bone "head". The angles of this bone are added to the view position of the player, so the code will detect the local orientation of this bone.
If this bone is not present, then the gun's anim will be like the old ones. This new bone should be the child of bone "origin", and it shouldn't have any child, to work properly.
With this hierarchy, the bone "head" will cause only the animation of the head, so the gun won't move.
Keep in mind that the orientation of this bone must be '0 0 0' in the default view. Also, the origin should be '0 0 0' too, just like the bone "origin". The code won't detect the origin of this bone, this mean that the head will be animated only by its current orientation.
This will help you to make the animation. You could link a camera to the bone "head", then assign one viewport to this camera.
Anyway, here the video I made to show you this stuff, http://www.youtube.com/watch?v=JVvaBVRf2gs
Here you can download the mod you saw in the video, http://www.mediafire.com/?xuy7c6ggx9sbo72
...And last but not least, I attach the source code, just search my name to see the stuff I implemented. Any suggestion will be appreciated